Vascular lesion treatment using a catheter is widely introduced since there is less surgical invasion. For example, in percutaneous transluminal coronary angioplasty, a balloon catheter is used to improve a blood flow by widening a lesion area of the coronary artery. In general, the balloon catheter has an elongated and hollow catheter shaft, a balloon disposed on a distal side of the catheter shaft, and a hub disposed on a proximal side of the catheter shaft.
As a structure of the balloon catheter, a known structure generally includes an over-the-wire type in which a guide wire is inserted from the proximal end into the distal of the catheter shaft and a rapid exchange type in which the guide wire is inserted into only the distal portion of the catheter shaft. In the rapid exchange type catheter, the guide wire is inserted into only the distal portion of the catheter shaft. Accordingly, a guide wire port for allowing the guide wire to pass therethrough is formed in an intermediate portion of the catheter shaft. A dilation lumen, which circulates a dilation fluid for dilating a balloon, is formed in the catheter shaft on the proximal side of the guide wire port. The dilation lumen and a guide wire lumen into which the guide wire is inserted are formed in parallel in the catheter shaft on the distal side of the guide wire port.
The catheter shaft having the guide wire port is manufactured as follows. First, a proximal side shaft, a distal side shaft, and an inner tube shaft are prepared. The inner tube shaft is inserted into a hollow interior of the distal side shaft. In a state where a proximal side terminal thereof is exposed from a proximal side terminal of the distal side shaft, the proximal side shaft, the distal side shaft, and the inner tube shaft are integrated with each other by means of thermal fusion-bonding. During the thermal fusion-bonding, core bar materials are respectively inserted into the hollow interior of the inner tube shaft serving as the guide wire lumen and the hollow interior of the distal side shaft serving as the dilation lumen. The respective shafts are fused using a thermally shrinkable tube.
When the catheter shaft is thermally fused, in order to restrain the guide wire lumen and the dilation lumen from communicating with each other or to prevent a portion between both of these from being thinned, a known technique is to dispose a connection tube in a proximal side end portion of the inner tube shaft, which forms the guide wire lumen. As the catheter having this catheter shaft, for example, JP-A-2014-195487 discloses a catheter.